Camshaft bearing caps or “cam caps” are conventionally used to secure a camshaft bearing assembly to an engine block. Cam caps come in various shapes, but typically include a portion of an arch with bolt holes on both sides. The camshaft bearing assembly is held in place in the engine by the arch of the cam cap when the cam cap is secured to the block by fastening bolts through the bolt holes of the cam cap to the block. As the camshaft rotates to engage the valve train, the cam caps must be able to withstand cyclic loading. It has become more common to form various engine components, including cam caps, from aluminum alloys because many aluminum alloys have excellent strength to weight ratios.
Many of these aluminum cam caps have been formed by die casting in the past. However, because the cam caps must provide a precision fit around the camshaft bearings when bolted to the block, many of the dimensions for cam caps have tight tolerances. Because die cast cam caps do not have the needed dimensional precision after casting, die cast cam caps must be subsequently machined. Machining the cam cap adds time and cost to the production of the cam cap. Further, some cam caps may have fine levels of detail, such as oil passageways, which are not easily formed by die casting.
To avoid many of these problems and to provide a cam cap that is more dimensionally accurate prior to machining, some aluminum cam caps are fabricated using powder metal processing. However, because cam caps fabricated by powder metal processing have higher levels of porosity when compared to die cast cam caps (which are typically fully dense), powder metal cam caps often have somewhat compromised mechanical properties in comparison to die cast cam caps.
Hence, there is a need for powder metal parts, such as cam caps, that have improved mechanical properties.